1. Technical Field
This invention generally relates to devices for restricting unauthorized users from placing certain telephone calls. In particular, this invention relates to a programmable telephone call restricting apparatus which can be placed directly in the telephone lines or housed within a telephone set.
2. Background Art
Unauthorized use of the telephone for placing toll calls has been a problem for quite some time. The recent increase in the number of businesses providing information services via toll lines, such as 900 numbers, has amplified the problem greatly. This has resulted in many telephone customers receiving large telephone bills due to unauthorized toll charges. Additionally, parents have to worry about the type of material their children have access to via an unrestricted telephone.
In the current state of the art several different methods are employed by call restriction apparatus. One such method, as disclosed in ROGERS, ET AL., Pat. No. 4,188,508, provides for restricting a telephone call based upon interpreting the first seven dialed digits and comparing them with a list of allowed numbers stored in a memory device. For toll calls, the acceptance or rejection of the call is based on allowed area codes and/or exchange prefixes. Consequently, the device is incapable of allowing or prohibiting individual telephone numbers.
A second device, as disclosed in HESTAD, ET AL., Pat. No. 4,232,200, teaches a microprocessor based repertory dialing system which has limited call restriction capabilities. In the call restriction mode, the device simply restricts all out-going toll calls unless a secret code is entered prior to dialing the telephone number. The secret code is installed into the apparatus by four electrical switches arranged in a binary configuration. The drawbacks to this device are that it does not provide for selective call restriction and that it is difficult to program the secret bypass code into the apparatus.
Another method for restricting telephone calls as taught in JACKSON, Pat. No. 4,012,602, is based on simply counting the number of digits contained in the dialed telephone number and restricting any calls containing more than a predetermined number of digits. Here again, the device is too restrictive and does not allow for the placement of authorized toll calls.
What is needed is a device which is easy to operate, relatively inexpensive, and allows for selective call restriction, thereby providing for a flexible call restricting device and further can be installed in a tamper free location.
Accordingly, it is an object of this invention to provide a call restricting apparatus which can be installed in the telephone lines and is capable of selectively restricting telephone calls. Another object of this invention is to provide a call restricting apparatus which is easy to program and does not require manipulation of hardware. Still another object of this invention is to provide a call restricting apparatus which is essentially self-contained and can be installed in an inconspicuous location such as within the telephone set, in a wall jack, or in the incoming telephone lines.